The present invention relates to stabilizer compositions for cellulose ester resin compositions and to cellulose ester resin compositions having improved resistance to degradation caused by heat. More particularly, the present invention relates to resin compositions containing organic acid esters of cellulose as a resin component and a stabilizer comprising nonylphenyl neopentylene phosphite as a stabilizer to improve the melt viscosity of the polymer during hot working and to minimize discoloration of the polymer when heated.
Numerous references disclose the preparation of phosphite esters and/or the use of phosphites to stabilize cellulose esters. For example, U.S. Pat. No. 2,834,798 is directed to novel phosphites and to methods of preparing phosphites. According to the '798 patent, such phosphites are effective plasticizers and stabilizers for vinyl chloride resins and other plastics.
U.S. Pat. No 3,047,608 discloses processes for the preparation of phosphite esters. According to the '608 patent, phosphite esters can be prepared by transesterification of certain aromatic phosphites with a desired alcohol in the presence of certain phosphite catalysts. The use of these phosphites and other phosphorous compounds to stabilize solid mono alfa olefin polymers is disclosed in U.S. Pat. No. 3,454,521.
U.K. Patent Specification No. 996,254 is directed to cellulose ester compositions containing certain neopentyl phosphites. According to the '254 patent, cellulose esters incorporating such neopentyl phosphites may be stabilized and offer appreciable resistance to color formation when exposed to heat.
U.S. Pat. No. 4,137,201 is directed to a thermal stabilizer system for cellulose esters. According to the '201 patent, a stabilizer system is provided for cellulose esters which comprises at least one cyclic phosphonite compound of a specified formula, a conventional antioxidant and an acid accepting epoxy compound.
U.S. Pat. No. 4,209,340 is directed to providing a cellulose organic acid ester composition comprising a cellulose organic acid ester and incorporating therein certain organic phosphite compounds to stabilize the resin against discoloration and degradation of physical properties caused by the influence of heat. According to the '340 patent, the organic phosphite compounds disclosed therein are effective to stabilize the resin against discoloration during hot molding and have a reduced tendency to promote reduction of the degree of polymerization but do not exhibit a substantial activity of improving the heat resistance or preventing oxidative degradation of the resin. Accordingly, the '340 patent suggests the use of known thermal stabilizers and antioxidants such as epoxy compounds, thioethers, phenol compounds and amine compounds in combination with the organic phosphite compound.
U.S. Pat. No. 4,357,168 which is a continuation-in-part of U.S. Pat. No. 4,256,505, is directed to cellulosic compositions comprising a cellulose ester or a cellulose ether, a surfactant and a heat stabilizer and optionally an oil extender. The '168 patent discloses cellulose ester formulations which include, among other components, a phosphite heat stabilizer and epoxidized soy bean oil.
U.S. Pat. No. 4,882,374 is directed to certain dioxaphosphorinane compounds and polyolefin materials stabilized therewith. According to the '374 patent, polyolefin materials, such as polypropylene which incorporate certain cyclic phosphites are stabilized against thermally-induced oxidative degradation.
A review of the above-mentioned patents and other literature directed to attempts to provide phosphites capable of stabilizing resins against degradation from heat, indicates there is still a need to provide a stabilizer composition which will increase the stability of resins, particularly cellulose ester resins, with respect to process and heat degradation.
Accordingly, it is general object of the present invention is to provide a stabilizer composition for cellulose carboxylic acid esters.
It is another object of the present invention to provide a method of stabilizing cellulose ester polymer resin compositions against heat degradation.
It is a further object of the present invention to provide novel stabilized cellulose ester polymers.
These and other objects of the present invention will be apparent to those skilled in the art from the following description.